1. Field of the Invention
The present invention relates to a sound reproducing apparatus and a method for providing a virtual sound source, and more particularly, to a sound reproducing apparatus for providing an optimal virtual sound source by converting sound signals inputted in multi-channels into at least more than one virtual sound source which is outputted thereafter.
2. Description of the Related Art
In the conventional audio industry field, it has been attempted to reproduce a sound that expresses presence vividly and accurately by creating a sound in a one-dimensional front direction or in a two-dimensional plane level. That is, the multimedia industry has been focused to develop a technology that allows acoustic information, more particularly, sound signals to be recorded and reproduced vividly and accurately along with provided visual information. Therefore, most of currently manufactured sound reproducing apparatuses are aimed at reproducing stereo sound signals instead of mono sound signals. However, when the stereo sound signals are reproduced, a range of perceiving actual presence by the reproduced sound signals is limited depending on allocation of speakers. For this reason, there are many studies on improving reproducibility of speakers to broaden the range of perceiving the actual presence and on generating virtual signals by signal processing.
As a result of these active studies, one representative system is a stereo surround sound system using five speakers. This sound system processes separately virtual signals outputted to speakers at the rear. A method for generating these virtual signals is to give a delay as signals move spatially, decrease sizes of the signals and then transmit these downsized signals to the rear side. Most currently manufactured sound reproducing apparatuses take a stereo sound system of Dolby Prologic Surround that allows a user to be able to experience a dynamic sound system as is found in a theater as long as there is a sound reproducing apparatus capable of reproducing Dolby Prologic Surround sounds.
Although an increase in the number of channels provides an effect on reproducing an improved quality of sound, the number of speakers needs to be increased as many as the number of channels. As a result, there are problems in increasing costs and requiring more spaces to install speakers.
These problems can be improved by applying the study about how humans hear sounds generated in a three-dimensional space. Particularly, there are numerous studies on the human auditory system that allows one to perceive a three-dimensional sound space, and thus, it is possible to create virtual sound sources recently. These virtual sound sources are applied in various fields.
In the case of applying the virtual sound source concept to sound reproducing apparatuses, that is, if it is possible to employ a predetermined number, for instance, two speakers instead of employing a larger number of speakers to provide multi-directional sound sources, it is greatly advantageous in realizing a sound reproducing apparatus with intended functions. It is economically advantageous by being able to employ the decreased number of speakers. Also, another advantage is that it is possible to reduce a space occupied by a sound system.
FIG. 1 is a diagram showing locations of virtual sound sources employed in a conventional sound reproducing apparatus.
In this drawing, virtual sound sources are outputted through frontal left and right speakers 10 and 12. In the case of applying the virtual sound sources to the conventional sound reproducing apparatus, a reference location of an actual sound source originated from a Dolby surround stereo sound reproducing apparatus is applied for determining locations of virtual sound sources 20, 22, 24, 26 and 28 by taking a user 30 as a reference point.
The above reference location can be an ideal sound reproducing location when a plurality of actual speakers, which are actual sound sources as being adopted in a stereo sound reproducing apparatus, are employed. However, because of a difficulty in artificially adjusting a location of sound toward a rear side due to a limitation in reproducing stereo sounds when the frontal left and right speakers 10 and 12 are solely used, this reference location can not be determined to be the best sound reproducing location in the stereo sound reproducing apparatus using only the frontal left and right speakers 10 and 12.
Also, virtual sound sources may have different optimal locations from each other depending on a type of each sound reproducing apparatus and an environment at which a sound reproducing apparatus is reproduced. However, for the conventional sound reproducing apparatus, the locations of the virtual sound sources are fixed to the locations in which the speakers of the Dolby surround stereo sound reproducing apparatus are placed. Hence, there may be a problem of adaptive allocation of the virtual sound sources.